Toyota Yaris: Seat Belt Warning System / Rear Seat Belt Warning Light Malfunction

Toyota Yaris XP210 (2020-2024) Reapir and Service Manual / Vehicle Interior / Seat Belt / Seat Belt Warning System / Rear Seat Belt Warning Light Malfunction

DESCRIPTION

The main body ECU (multiplex network body ECU) detects whether either the rear doors are open or closed based on the courtesy light switch condition and then sends the rear door status signal to the combination meter assembly.

The power distribution box assembly detects whether either the rear seat belts are fastened or unfastened based on the rear seat belt buckle switch condition and then sends the rear seat belt buckle switch status signal to the combination meter assembly.

The combination meter assembly illuminates, blinks or turns off the rear seat belt warning light on the combination meter assembly in accordance with the vehicle speed, rear seat belt state and front door state.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

The seat belt warning system uses the CAN communication system and CXPI communication system. First, confirm that there is no malfunction in the CAN communication system. Refer to the How to Proceed with Troubleshooting procedure.
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Before replacing the main body ECU (multiplex network body ECU), refer to Registration.
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When replacing the combination meter assembly, always replace it with a new one. If a combination meter assembly which was installed to another vehicle is used, the information stored in it will not match the information from the vehicle and a DTC may be stored.

PROCEDURE

1.	READ VALUE USING GTS (REAR SEAT RH BUCKLE SWITCH STATUS / REAR SEAT LH BUCKLE SWITCH STATUS)

(a) Read the Data List according to the display on the GTS.

Body Electrical > Power Distribution Box > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Rear Seat RH Buckle Switch Status	Rear RH seat belt buckle switch status	Set/Unset/Unknown	Set: Rear RH seat belt fastened Unset: Rear RH seat belt not fastened	-
Rear Seat LH Buckle Switch Status	Rear LH seat belt buckle switch status	Set/Unset/Unknown	Set: Rear LH seat belt fastened Unset: Rear LH seat belt not fastened	-

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Rear Seat RH Buckle Switch Status

Rear RH seat belt buckle switch status

Set/Unset/Unknown

Set: Rear RH seat belt fastened

Unset: Rear RH seat belt not fastened

Rear Seat LH Buckle Switch Status

Rear LH seat belt buckle switch status

Set/Unset/Unknown

Set: Rear LH seat belt fastened

Unset: Rear LH seat belt not fastened

Body Electrical > Power Distribution Box > Data List

Tester Display
Rear Seat RH Buckle Switch Status
Rear Seat LH Buckle Switch Status

OK:

The GTS display changes correctly in response to the rear seat belt buckle switch condition.

Result	Proceed to
OK	A
NG (Rear RH seat belt malfunction)	B
NG (Rear LH seat belt malfunction)	C

REPLACE COMBINATION METER ASSEMBLY

GO TO STEP 4

2.	INSPECT REAR SEAT INNER BELT ASSEMBLY RH

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INSPECT REAR SEAT INNER BELT ASSEMBLY RH

3.	CHECK HARNESS AND CONNECTOR (REAR SEAT INNER BELT ASSEMBLY RH - POWER DISTRIBUTION BOX AND BODY GROUND)

(a) Disconnect the O19 rear seat inner belt assembly RH connector.

(b) Disconnect the 4E power distribution box assembly connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
O19-5 (RBR+) - 4E-8	Always	Below 1 Ω
O19-5 (RBR+) or 4E-8 - Body ground	Always	10 kΩ or higher
O19-4 (RBR-) - Body ground	Always	Below 1 Ω

REPLACE POWER DISTRIBUTION BOX ASSEMBLY

REPAIR OR REPLACE HARNESS OR CONNECTOR

4.	INSPECT REAR SEAT INNER BELT ASSEMBLY LH

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INSPECT REAR SEAT INNER BELT ASSEMBLY LH

5.	CHECK HARNESS AND CONNECTOR (REAR SEAT INNER BELT ASSEMBLY LH - POWER DISTRIBUTION BOX AND BODY GROUND)

(a) Disconnect the O20 rear seat inner belt assembly LH connector.

(b) Disconnect the 4E power distribution box assembly connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
O20-5 (LBR+) - 4E-19	Always	Below 1 Ω
O20-5 (LBR+) or 4E-19 - Body ground	Always	10 kΩ or higher
O20-4 (LBR-) - Body ground	Always	Below 1 Ω

REPLACE POWER DISTRIBUTION BOX ASSEMBLY

REPAIR OR REPLACE HARNESS OR CONNECTOR

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